GWT 2.0 using tomcat in hosted mode

I am exploring the features of GWT2.0. One of the feature seems to be using a server of our preference in the hosted mode, rather than the inbuilt jetty that comes with GWT. I have been trying to do this with no success. I read through the documentation here and searched but I am unable to do it or should I say I dont understand how to do it.

To make things more clear, I want to do the same debugging and stuff that I am able to do with Jetty, with my external container also.

Can someone please explain? And also when I run an application with Jetty I get the url appended with a parameter '?gwt.codesvr=<some port no>' . What is the significance of this?